As examples of a conventional video navigation apparatus, there have been known a navigation apparatus disclosed in Japanese Patent Application Laid-open No. 9-33271 (publication 1), and a car navigation system disclosed in Japanese Patent Application Laid-open No. 11-108684 (publication 2). A principle that is common to the video navigation apparatuses in the publications 1 and 2 is shown in FIG. 23.
In FIG. 23, a position and angle sensor 1 detects a position and angles of a camera 2. As a position sensor, there is, for example, a sensor that knows a current position by using a GPS (Global Positioning System) satellite. Further, as an angle sensor, there are a one that utilizes magnetism, a one that utilizes the principle of gyro, and a one that combines these.
Position information that shows a position and angle information that shows angles of the camera 2 detected by the position and angle sensor 1 are stored in a position and angle information storing unit 3. The camera 2 is mounted on a vehicle, and takes a scene in front of the vehicle as image information, and stores this into a scenery image storing unit 4. Indication information (information such as an arrow mark, a symbol, and a character) of a proceeding direction to be provided to a user is generated mechanically or artificially, and is stored into an indication information storing unit 5. An indication image generating unit 6 processes position information and angle information stored in the position and angle information storing unit 3, based on the indication information stored in the indication information storing unit 5. At the same time, the indication image generating unit 6 combines a result of this processing and scenery image data stored in the scenery image storing unit 4 and stores it into a display unit 7.
Based on the principle, it is possible to guide a user to a target place by using an image that has an arrow mark, a symbol and characters embedded in an actual scene.
However, according to the conventional video navigation apparatus, it is necessary to install the position and angle sensor 1 that is an angle sensor in addition to a position sensor. Therefore, there has been a problem that the apparatus becomes large and heavy. Particularly, when a video navigation is carried out by using a portable telephone or a portable information terminal, it is necessary to make the apparatus small and light to enable the user to easily carry the apparatus. However, there has been a problem that it is difficult to install the position and angle sensor 1 and also obtain a compact and light apparatus suitable for carrying.
When a GPS is utilized as a position sensor, for example, there has been a problem that it is not possible to know a correct position at a position like in a tunnel or a shade of a building where a wave of a GPS satellite does not reach. Therefore, when such an error occurs in the position and angle sensor 1, there arises a deviation in the positions of an arrow mark, a symbol and characters that the estimate image generating unit 6 embeds into the actual scene, according to this error. Therefore, there has been a problem that the user is misled to a wrong direction.
For a subject that it is desired to accurately know a current position of the camera, a car navigation apparatus disclosed in Japanese Patent Application Laid-open No. 9-152348 (publication 3) has been known, for example. In this publication 3, there is disclosed a method of comparing an image prepared in advance with an image (a camera image) picked up with a camera, and correcting an error in a result of measurement using a GPS or the like based on a result of this comparison. This method is for estimating a camera position by collating a specific pattern (generally called a template) registered in advance such as a signal mechanism or a road sign with a camera image. In other words, based on a pattern matching, first a part image that coincides with the template is found from the camera image. Next, when a part that coincides with the template has been found, a distance from the camera to a signal mechanism or a road sign is estimated based on a size of the part image. In general, when the knowledge that a signal mechanism or a road sign is installed at the crossing is used, it is possible to estimate a position of the camera based on the information relating to a position of the crossing.
However, according to the method of correcting a measured result disclosed in the publication 3, the following problems occur. At a position where an object that becomes a mark having substantially a fixed shape like a signal mechanism or a road sign exists, it is possible to estimate a camera position based on this object. However, at a position where it is not possible to set an object having substantially a fixed shape like a signal mechanism or a road sign as a mark, it is not possible to estimate a camera position.
According to the method of correcting an error of a measured result, it is necessary to search for a part image that coincides with a plurality of templates set in advance from the camera image that changes each moment. However, when a search range becomes large, the processing quantity of pattern matching processing increases, and precision tends to become lower. Consequently, according to the method of correcting an error of a measured result, there has been a problem that it is hard to process the pattern matching in a short time and in high precision.
Therefore, it is a first object of this invention to provide a video navigation apparatus that can guide a user by properly embedding indication information such as an arrow mark, a symbol and characters into an actual scene, by estimating position information and angle information of a camera in a short time and in high precision, using information of only one sensor out of an angle sensor and a position sensor, or using information including errors from the position and position sensors.
It will be considered that a conventional video navigation apparatus including the video navigation apparatuses described in the publications 1 and 2 is mounted on a work vehicle such as a forklift, a crane truck, and a bulldozer, and that a work procedure is indicated to a driver. It is usual that these work vehicles work within a predetermined area, and therefore, these vehicles repeatedly pass the same point frequently. However, according to the conventional video navigation apparatus, indication information such as an arrow mark is corresponded to a specific point in advance. Therefore, when a procedure is to make a left turn at the first time and make a right turn at the second time at the same point A, for example, both an arrow mark of the left turn and an arrow mark of the right turn are displayed at the point A. Consequently, there is a problem that it is not possible to give proper guidance.
Therefore, it is a second object of this invention to provide a video navigation apparatus that can indicate a series of work procedure following this order.